Cancer is the major health problem threatening human lives. Hepatocellular carcinoma (HCC) is one of the most serious among cancer diseases. It is reported that the new cases of primary hepatocellular carcinoma exceeds over one million worldwide each year. 70% of the new cases occur in Asia, and about 40-45% of the worldwide new cases occur in China. The total number of new hepatocellular carcinoma cases every year in China is about 450,000, and the number is increasing, especially in those between ages 20-60. The high incidence, difficulty in early diagnosis, fast growing rate, high reoccurrence, and the high mortality rate make HCC a most malignant cancer. Most HCC patients have already progressed to the intermediate stage or late stage when diagnosed, and they can only survive for 3-6 months if without a proper treatment.
To elucidate the mechanism underlying cancerogenesis would help for cancer prevention, diagnosis and treatment. Early diagnosis is crucial for raising the curative rate and reducing the mortality. Currently used HCC-diagnostic marker, the serum AFP, has 30% of negative results in HCC patients, while some benign liver disease can cause a significant increase of AFP level in serum, creating some difficulty in differential diagnosis. It has been found that the hepatocarcinogenesis is related to individual hereditary susceptibility. Individuals with different genetic backgrounds possess different handling capability toward environmental carcinogens. This leads to different risk of suffering from cancer for individuals. It is the various genotypes and the genetic diversity that cause the different genetic susceptibility for cancerogenesis.
Cancer is essentially a cellular hereditary disease. Although a great number of cancer-related genes have been discovered, the mechanisms of the cancerogenesis and the development remain to be elucidated. The known oncogenes can be divided into five categories according to the cellular localization and function of their encoded proteins: I. genes that encode growth factors, including sis, int-2, hst, fgf-5; II. genes that encode growth factor receptors, including erbB, erbB-2, fins, met, ros, and others; III. genes that encode signal transduction molecules in cytoplasm, including abl, src, ras, raf, yes, fgr, fes, lck, mos, and others; IV. genes that encode regulatory molecules for cell proliferation and apoptosis, including bcl-1, bcl-2 and others; and V. genes that encode the nuclear DNA-binding proteins (transcription factors), such as myc, myb, fos, jun, B-lym, ski, ets, rel and others. It has been demonstrated that ras, src, myc, met and p53 etc. are the genes closely associated with HCC.